the Semaphore class provides Binary & Counting semaphore objects, based on BlockingObject base class. More...

#include <ksemaphore.h>

Inheritance diagram for Mark3::Semaphore:

Public Member Functions
void *	operator new (size_t sz, void *pv)

	~Semaphore ()

void	Init (uint16_t u16InitVal_, uint16_t u16MaxVal_)
	Initialize a semaphore before use. Must be called before attempting post/pend operations on the object. More...

bool	Post ()
	Increment the semaphore count. If the semaphore count is zero at the time this is called, and there are threads blocked on the object, this will immediately unblock the highest-priority blocked Thread. More...

void	Pend ()
	Decrement the semaphore count. If the count is zero, the calling Thread will block until the semaphore is posted, and the Thread's priority is higher than that of any other Thread blocked on the object. More...

uint16_t	GetCount ()
	Return the current semaphore counter. This can be usedd by a thread to bypass blocking on a semaphore - allowing it to do other things until a non-zero count is returned, instead of blocking until the semaphore is posted. More...

bool	Pend (uint32_t u32WaitTimeMS_)
	Decrement the semaphore count. If the count is zero, the thread will block until the semaphore is pended. If the specified interval expires before the thread is unblocked, then the status is returned back to the user. More...

void	WakeMe (Thread *pclChosenOne_)
	Wake a thread blocked on the semaphore. This is an internal function used for implementing timed semaphores relying on timer callbacks. Since these do not have access to the private data of the semaphore and its base classes, we have to wrap this as a public method - do not used this for any other purposes. More...

Public Member Functions inherited from Mark3::BlockingObject
	BlockingObject ()

	~BlockingObject ()

Private Member Functions
uint8_t	WakeNext ()
	Wake the next thread waiting on the semaphore. Used internally. More...

bool	Pend_i (uint32_t u32WaitTimeMS_)
	Pend_i. More...

Private Attributes
uint16_t	m_u16Value
	Current count held by the semaphore. More...

uint16_t	m_u16MaxValue
	Maximum count that can be held by this semaphore. More...

Additional Inherited Members
Protected Member Functions inherited from Mark3::BlockingObject
void	Block (Thread *pclThread_)
	Block Blocks a thread on this object. This is the fundamental operation performed by any sort of blocking operation in the operating system. All semaphores/mutexes/sleeping/messaging/etc ends up going through the blocking code at some point as part of the code that manages a transition from an "active" or "waiting" thread to a "blocked" thread. More...

void	BlockPriority (Thread *pclThread_)
	BlockPriority Same as Block(), but ensures that threads are added to the block-list in priority-order, which optimizes the unblock procedure. More...

void	UnBlock (Thread *pclThread_)
	UnBlock Unblock a thread that is already blocked on this object, returning it to the "ready" state by performing the following steps: More...

void	SetInitialized (void)
	SetInitialized. More...

bool	IsInitialized (void)
	IsInitialized. More...

Protected Attributes inherited from Mark3::BlockingObject
ThreadList	m_clBlockList

uint8_t	m_u8Initialized

Static Protected Attributes inherited from Mark3::BlockingObject
static constexpr auto	m_uBlockingInvalidCookie = uint8_t { 0x3C }

static constexpr auto	m_uBlockingInitCookie = uint8_t { 0xC3 }

Detailed Description

the Semaphore class provides Binary & Counting semaphore objects, based on BlockingObject base class.

Examples:: lab4_semaphores/main.cpp, lab6_timers/main.cpp, and lab9_dynamic_threads/main.cpp.

Definition at line 36 of file ksemaphore.h.

Constructor & Destructor Documentation

◆ ~Semaphore()

Mark3::Semaphore::~Semaphore ( )

Definition at line 58 of file ksemaphore.cpp.

Member Function Documentation

◆ GetCount()

uint16_t Mark3::Semaphore::GetCount ( )

Return the current semaphore counter. This can be usedd by a thread to bypass blocking on a semaphore - allowing it to do other things until a non-zero count is returned, instead of blocking until the semaphore is posted.

Returns: The current semaphore counter value.

Definition at line 206 of file ksemaphore.cpp.

◆ Init()

void Mark3::Semaphore::Init	(	uint16_t	u16InitVal_,
		uint16_t	u16MaxVal_
	)

Initialize a semaphore before use. Must be called before attempting post/pend operations on the object.

This initialization is required to configure the behavior of the semaphore with regards to the initial and maximum values held by the semaphore. By providing access to the raw initial and maximum count elements of the semaphore, these objects are able to be used as either counting or binary semaphores.

To configure a semaphore object for use as a binary semaphore, set values of 0 and 1 respectively for the initial/maximum value parameters.

Any other combination of values can be used to implement a counting semaphore.

Parameters

u16InitVal_	Initial value held by the semaphore
u16MaxVal_	Maximum value for the semaphore. Must be nonzero.

Examples:: lab6_timers/main.cpp, and lab9_dynamic_threads/main.cpp.

Definition at line 94 of file ksemaphore.cpp.

◆ operator new()

void* Mark3::Semaphore::operator new	(	size_t	sz,
		void *	pv
	)

inline

Definition at line 39 of file ksemaphore.h.

◆ Pend() [1/2]

void Mark3::Semaphore::Pend ( )

Decrement the semaphore count. If the count is zero, the calling Thread will block until the semaphore is posted, and the Thread's priority is higher than that of any other Thread blocked on the object.

Examples:: lab4_semaphores/main.cpp.

Definition at line 194 of file ksemaphore.cpp.

◆ Pend() [2/2]

bool Mark3::Semaphore::Pend ( uint32_t u32WaitTimeMS_ )

Decrement the semaphore count. If the count is zero, the thread will block until the semaphore is pended. If the specified interval expires before the thread is unblocked, then the status is returned back to the user.

Returns: true - semaphore was acquired before the timeout false - timeout occurred before the semaphore was claimed.

Definition at line 200 of file ksemaphore.cpp.

◆ Pend_i()

bool Mark3::Semaphore::Pend_i ( uint32_t u32WaitTimeMS_ )

private

Pend_i.

Internal function used to abstract timed and untimed semaphore pend operations.

Parameters

u32WaitTimeMS_ Time in MS to wait

Returns: true on success, false on failure.

Definition at line 152 of file ksemaphore.cpp.

◆ Post()

bool Mark3::Semaphore::Post ( )

Increment the semaphore count. If the semaphore count is zero at the time this is called, and there are threads blocked on the object, this will immediately unblock the highest-priority blocked Thread.

Note that if the priority of that Thread is higher than the current thread's priority, a context switch will occur and control will be relinquished to that Thread.

Returns: true if the semaphore was posted, false if the count is already maxed out.

Examples:: lab4_semaphores/main.cpp, and lab6_timers/main.cpp.

Definition at line 108 of file ksemaphore.cpp.

◆ WakeMe()

void Mark3::Semaphore::WakeMe ( Thread * pclChosenOne_ )

Wake a thread blocked on the semaphore. This is an internal function used for implementing timed semaphores relying on timer callbacks. Since these do not have access to the private data of the semaphore and its base classes, we have to wrap this as a public method - do not used this for any other purposes.

Definition at line 68 of file ksemaphore.cpp.

◆ WakeNext()

uint8_t Mark3::Semaphore::WakeNext ( )

private

Wake the next thread waiting on the semaphore. Used internally.

Definition at line 78 of file ksemaphore.cpp.

Member Data Documentation

◆ m_u16MaxValue

uint16_t Mark3::Semaphore::m_u16MaxValue

private

Maximum count that can be held by this semaphore.

Definition at line 140 of file ksemaphore.h.

◆ m_u16Value

uint16_t Mark3::Semaphore::m_u16Value

private

Current count held by the semaphore.

Definition at line 139 of file ksemaphore.h.

The documentation for this class was generated from the following files:

/mnt/c/Users/moslevin/m3-repo2/kernel/src/public/ksemaphore.h
/mnt/c/Users/moslevin/m3-repo2/kernel/src/ksemaphore.cpp

Public Member Functions

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ ~Semaphore()

Member Function Documentation

◆ GetCount()

◆ Init()

◆ operator new()

◆ Pend() [1/2]

◆ Pend() [2/2]

◆ Pend_i()

◆ Post()

◆ WakeMe()

◆ WakeNext()

Member Data Documentation

◆ m_u16MaxValue

◆ m_u16Value